Phosphorus-free sulfide solid electrolyte

ABSTRACT

A solid electrolyte material having a general chemical formula of Li2+xM2+xM′1−xS6, where M is at least one of Al, Ga or In, M′ is at least one of Si or Ge, and 0&lt;x≤0.5. The solid electrolyte material according to the application is simple in composition, contains no phosphorus sensitive to water, and has good Li+ conductivity at the same time.

CROSS REFERENCE TO THE RELATED APPLICATIONS

The application is a Continuation of PCT/CN2019/124604 filed on Dec. 11,2019 which claims the benefit of priority from Chinese patentapplication 201911061250.5 filed on Nov. 1, 2019, the disclosure ofwhich is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The invention relates to a phosphorus-free sulfide solid electrolyte.

BACKGROUND

As the electronic technique rapidly develops, electronic equipment suchas phones, notebook computers, vidicon and electric tools increases, andpeople's demand for energy storage power is getting higher. It is urgentto develop secondary batteries with high capacity, long life, and goodsafety performance. In contrast with lead-acid, nickel-cadmium,nickel-hydrogen batteries, or the like, lithium-ion batteries arecharacterized in high energy density, high power density, long life,good safety, low self-discharge rate, and wide temperature adaptationrange, thereby being most widely used. However, it is required to use aflammable organic solution as an electrolyte for traditional lithium-ionbatteries, so a great potential safety hazard exists. Particularly, forlithium-ion batteries with higher energy density, although measures canbe taken to improve material, electrode, cell, module, power management,heat management, systematic design, or the like, battery safety stillremains prominent and it is hard to completely avoid thermal runaway. Inrecent years, vicious battery explosion accidents sometimes happen.Therefore, it is especially important to explore lithium-ion secondarybatteries with good safety performance.

In order to solve the above safety problem fundamentally, it is a goodscheme to replace an organic electrolyte solution with a solidelectrolyte. The solid electrolyte is incombustible, non-volatile, andfree from corrosion and liquid leakage, therefore, an all-solid-statebattery assembled with the solid electrolyte has extremely high safety.In addition, an all-solid-state battery is characterized in long lifeand high theoretical energy density. During the use of lithium-ionbatteries with the organic electrolyte solution, since an SEI film getsbroken and is generated repeatedly during the cyclic process, resultingin accelerating the degradation of battery capacity, and lots of sideeffects during the cyclic process also have a severe impact on theservice life of batteries, the solid electrolyte can solve this problem.In another aspect, most of the solid electrolytes are featured with goodmechanical strength and can inhibit lithium dendrites effectively. Thiscan also significantly improve the cycle performance and service life ofbatteries. In addition, since the solid electrolyte generally has a wideelectrochemical window, it can match with more high-voltage positiveelectrodes; moreover, the all-solid-state battery can greatly simplifythe battery thermal management system and can greatly improve the energydensity.

In recent years, researchers have conducted a lot of exploratory work onthe solid electrolyte. In summary, there are three types of common solidelectrolytes at present: polymer-type, oxide-type and sulfide-type. Theconcept of polymer solid electrolyte was firstly put forward by Armandin 1978. The polymer solid electrolyte includes a polymer and a lithiumsalt. Lithium ions and polar groups in a polymer chain are complexingwith each other. Under the action of an external electric field, theflexibility of the polymer chain is used for the directional migrationof lithium ions. Common polymer solid electrolytes include PEO-based,PPO-based, PAN-based, PMMA-based, and PVDF-based electrolytes, or thelike. These kinds of electrolytes have light mass, good viscoelasticity,and good mechanical processability, but very low ionic conductivity hasa severe impact on the high-rate charge and discharge capacity ofbatteries. Chemical copolymerization, grafting, or the like are usuallyused to reduce the crystallinity of a polymer matrix and improve theionic conductivity, but improved room temperature ionic conductivity isstill very low. Oxide solid electrolytes include Perovskite-type (e.g.,Li_(3x)La_(2/3−x)TiO₃), Anti-Perovskite-type (e.g., Li₃OCl),NASICON-type (e.g., Li_(1+x)Al_(x)Ti_(2−x)(PO₄)₃), Garnet-type (e.g.,Li₇La₃Zr₂O₁₂) electrolytes, or the like. These kinds of electrolytesgenerally have good chemical stability and can exist in the air stably,but the ionic conductivity is relatively low, the grain boundaryresistance is great, and the compatibility with an electrode is poor.Compared with two types of solid electrolytes aforesaid, the sulfidesolid electrolyte is characterized in high ionic conductivity, low grainboundary resistance, good electrochemical stability, or the like,receives wide attention from researchers, and is the material that ismost promising for scale application. In the sulfide materials,Li₂S—SiS₂ system is a type of solid electrolyte that is first studied.It is reported that (Hayashi et al., “Characterization ofLi₂S—SiS₂-Li₃MO₃ M=B, Al, Ga and In) oxysulfide glasses and theirapplication to solid state lithium secondary batteries”, 2002, SolidState Ionics, Volume 152-153, Pages 285-290): Li₃PO₄, LiSiO₄, Li₃BO₃,and Li₃AlO₃ with glassy-state Li₂S—SiS₂ can significantly improve theconductivity and inhibit crystallization of materials. In 2001,Tatsumisago, et al. (Tatsumisago et al., “Solid state lithium secondarybatteries using an amorphous solid electrolyte in the system(100−x)(0.6Li₂S-0.4SiS₂).xLi₄SiO₄ obtained by mechanochemicalsynthesis”, 2001, Solid State Ionics, Volume 140, Pages 83-87) usedmechanical ball milling instead of melt quenching to prepare aglassy-state solid electrolyte (100−x)(0.6Li₂S-0.4SiS₂).xLi₄SiO₄, andexhaustively discussed the impact of milling time on the formation of aglassy state and the performance of all-solid-state batteries.Subsequently, Tatsumisago, et al. (Tatsumisago et al., “New, HighlyIon-Conductive Crystals Precipitated from Li₂S—P₂S₅ Glasses”, 2005,Advanced Materials, Volume 17, Pages 918-921) reported for the firsttime in 2005 the preparation of sulfur phosphorus compound material70Li₂S-30P₂S₅ by energetic ball milling, with the room temperature ionicconductivity up to 3.2×10⁻³ S/cm, thereby starting a trend of preparingglass-ceramic sulfur phosphorus compound materials by energetic ballmilling. In 2011, Tokyo Institute of Technology and Toyota MotorCorporation made a breakthrough (Kamaya et al., “A lithium superionicconductor”, 2011, Nature Materials, Volume 10, Pages 682-686). Theyjointly reported a crystal sulfur phosphide electrolyte with alithium-ion three-dimensional diffusion channel, Li₁₀GeP₂Si₂ (LGPS), onnature materials, a top international journal of materials science. Theroom temperature ionic conductivity reaches 1.2×10⁻² S/cm, which evencan be comparable to the ionic conductivity of common carbonateelectrolyte solution, thereby further attracting global attention tosulfur phosphorus compound materials. However, in another aspect, sulfurphosphorus compounds are generally sensitive to water in the air, andcan easily generate malodorous H₂S gas due to water absorption duringthe processing in a conventional environment. The gas is harmful to theenvironment and processing personnel. According to the Hard-SoftAcid-Base theory, P⁵⁺ in the sulfur phosphorus compounds is hard acid,and compared with S²⁻, O²⁻ in water is harder base. Hard acid reactswith hard base firstly, thus sulfides with phosphorus may deteriorateeasily when they absorb water. In view of this, exploration of somenovel sulfide solid electrolyte materials with good Li+ conductivity andwithout phosphorus is of great importance.

SUMMARY

The application provides a novel sulfide solid electrolyte material andan electrochemical device comprising the solid electrolyte material. Thesolid electrolyte material is simple in composition, contains nophosphorus sensitive to water, and has good Li⁺ conductivity at the sametime. It is a promising solid electrolyte material.

A first purpose of the application is to disclose a novel sulfide solidelectrolyte material.

A second purpose of the application is to disclose the crystallographiccharacteristics, structural information, XRD spectrogram, PBE band gap,Li⁺ migration path, and migration barrier of the solid electrolytematerial.

Specifically, the application discloses a novel sulfide solidelectrolyte material, represented by a general chemical formulaLi_(2+x)M^(2+x)M′_(1−x)S₆, wherein M is at least one of Al, Ga or In, M′is at least one of Si or Ge, and 0<x≤0.5.

First, the Li_(2+x)M_(2+x)M′_(1−x)S₆ material has diamond-likestructural characteristics. In the structure, coordination of M³⁺ (e.g.,Al³⁺) and M′⁴⁺ (e.g., Si⁴⁺) with S²⁻ forms tetrahedrons. All connectedcorner-sharing tetrahedrons form a three-dimensional network, and Li⁺ isfilled in the gap between tetrahedrons.

Next, the application discloses XRD spectrogram characteristics ofLi_(2+x)M_(2+x)M′_(1−x)S₆. In an XRD spectrogram, strong diffractionpeaks may occur at about 14.5°±3°, 15.5°±3°, 17°±3°, 25.5°±3°, 31.5°±3°,53.0°±3°, or the like.

Then, by taking Li_(2+x)Al_(2+x)Si_(1−x)S₆ as a demonstrative exampleand using VASP software (Hafner research group of University of Vienna,Vienna Ab-initio Simulation Package) for calculation, a PBE band gap ofthe Li_(2+x)Al_(2+x)Si_(1−x)S₆ material is no less than 2.8 eV. It iswell-known that exchange-correlation functional in the form of PBE mayseverely underestimate the optical band gap of insulators andsemiconductors (refer to the patent document, publication number:CN106684437A), and the intrinsic band gap of theLi_(2+x)Al_(2+x)Si_(1−x)S₆ material should be far beyond 2.8 eV. In2012, Yin Wenlong, et al. (Yin et al., “Synthesis, Structure, andProperties of Li₂In₂MQ₆ (M=Si, Ge; Q=S, Se): A New Series of IRNonlinear Optical Materials”, 2012, Inorganic Chemistry, Volume 51,Pages 5839-5843) firstly reported the experimental band gap ofLi₂In₂SiS₆ is about 3.61 eV. In the application, Li₂In₂SiS₆ iscalculated with the same parameters, and the PBE band gap is 2.08 eV. Itcan be seen from this that the intrinsic band gap ofLi_(2+x)Al_(2+x)Si_(1−x)S₆ should exceed about 4.3 eV.

Finally, by taking Li_(2+x)Al_(2+x)Si_(1−x)S₆ as an example, theapplication exhaustively evaluates lithium-ion migration paths andmigration barriers of Li_(2.125)Al_(2.125)Si_(0.875)S₆,Li_(2.25)Al_(2.25)Si_(0.75)S₆, and Li_(2.5)Al_(2.5)Si_(0.5)S₆.

Compared with the prior art, the invention has the following beneficialeffects:

The invention provides a novel sulfide solid electrolyte materialLi_(2+x)M_(2+x)M′_(1−x)S₆, with a diamond-like structure, wherecoordination of M³⁺ and M′⁴⁺ with four S²⁻ forms [MS₄] and [M′S₄]tetrahedrons. All corner-sharing tetrahedrons are connected, and Li⁺ isfilled in the gap between tetrahedrons.

This kind of material has a wide optical band gap. Particularly, for theLi_(2+x)Al_(2+x)Si_(1−x)S₆ material, the intrinsic band gap is no lessthan about 4.3 eV, and Li⁺ migration barrier is no greater than 0.45 eV.Overall, this kind of material has a wide band gap and a low Li⁺conduction barrier, indicating that it has strong Li⁺ conducting powerand is a novel fast lithium-ion conductor material, with a goodapplication prospect.

More importantly, compared with sulfur phosphorus family solidelectrolytes, according to the Hard-Soft Acid-Base theory, this kind ofmaterial does not contain hard acid P⁵⁺ and should have good stability.At the same time, it can be seen from the structure that alltetrahedrons are corner-sharing connected, groups are arranged compactlywith a little gap, and the structural stability is good.

In some embodiments, the general chemical formula of the solidelectrolyte material is Li_(2+x)M_(2+x)M′_(1−x)S₆, wherein M is at leastone of Ga or In, M′ is at least one of Si or Ge, and 0<x≤0.5.

In some embodiments, the general chemical formula of the solidelectrolyte material is Li_(2+x)Al_(2+x)Si_(1−x)S₆, wherein 0<x≤0.5.

In some embodiments, lattice parameters of the solid electrolytematerial are about a=13.0±2.0 Å, b=8.0±2.0 Å, c=13.0±2.0 Å, α=90.0°±5°,β=110.0°±10°, and γ=90.0°±5°.

In some embodiments, lattice parameters of the solid electrolytematerial are about a=12.0±1.0 Å, b=7.0±1.0 Å, c=12.0±1.0 Å, α=90.0°±5°,β=105°±5°, and γ=90.0°±5°.

In some embodiments, coordination of M³⁺ (Al³⁺) and M′⁴⁺ (Si⁴⁺) in thesolid electrolyte material structure with S²⁻ forms [MS₄] ([AlS₄]) and[M′S₄] ([SiS₄]). All corner-sharing tetrahedrons are connected, and Li⁺is filled in the gap between tetrahedrons.

In some embodiments, strong diffraction peaks may occur at about14.5°±3°, 15.5°±3°, 17°±3°, 25.5°±3°, 31.5°±3°, 53.0°±3°, or the like inXRD spectrogram of the solid electrolyte material.

In some embodiments, Li⁺ migration barrier of the solid electrolytematerial is no greater than about 0.45 eV.

In some embodiments, the PBE band gap of the solid electrolyte materialis no less than about 2.80 eV.

Unprecedented attention is paid to the safety of batteries. The solidelectrolyte material can replace the organic electrolyte solution and isapplied to novel lithium-ion batteries. The safety risks arising fromthermal runaway are thermal runaways in principle. The inventionprovides a type of novel sulfide solid electrolyte, with greatapplication potential. The solution is of high innovation and practicalvalue, and can promote the further application of sulfide solidelectrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a lattice structure and a Li⁺ migration path ofLi_(2.125)Al_(2.125)Si_(0.875)S₆.

FIG. 2 illustrates an XRD spectrogram ofLi_(2.125)Al_(2.125)Si_(0.875)S₆.

FIG. 3 illustrates a state density of Li_(2.125)Al_(2.125)Si_(0.875)S₆.

FIG. 4 illustrates a gap Li⁺ migration barrier ofLi_(2.125)Al_(2.125)Si_(0.875)S₆.

FIG. 5 illustrates a lattice structure and a Li⁺ migration path ofLi_(2.25)Al_(2.25)Si_(0.75)S₆.

FIG. 6 illustrates an XRD spectrogram of Li_(2.25)Al_(2.25)Si_(0.75)S₆.

FIG. 7 illustrates a state density of Li_(2.25)Al_(2.25)Si_(0.75)S₆.

FIG. 8 illustrates a gap Li⁺ migration barrier ofLi_(2.25)Al_(2.25)Si_(0.75)S₆.

FIG. 9 illustrates a lattice structure and a Li⁺ migration path ofLi_(2.5)Al_(2.5)Si_(0.5)S₆.

FIG. 10 illustrates an XRD spectrogram of Li_(2.5)Al_(2.5)Si_(0.5)S₆.

FIG. 11 illustrates a state density of Li_(2.5)Al_(2.5)Si_(0.5)S₆.

FIG. 12 illustrates a gap Li⁺ migration barrier ofLi_(2.5)Al_(2.5)Si_(0.5)S₆.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will be described below byreference to the figures. The exemplary embodiments are theinterpretation of the invention, instead of limiting the scope ofprotection of the claims of the invention. The scope of the invention isonly defined by the claims attached and equivalents thereof.

I. Solid Electrolyte Material

In general, inorganic solid electrolyte material usually comprises astable ion skeleton and a moveable ion (e.g., Li⁺). Compared with oxidesolid electrolytes, the ionic radius of S²⁻ in the sulfide solidelectrolytes is much greater than O²⁻, enabling a much larger movablespace for Li⁺ between skeletons; at the same time, the nucleus of S²⁻has a lower constraint to the ambient electron cloud, making that theelectron cloud is more easily polarized and the charge distribution maycooperate with Li⁺ more easily during the movement of Li⁺ to formdeformation and reduce the force on lithium-ion, thereby reducing themigration barrier of Li⁺. On the basis of fully understanding thestructural characteristics of sulfide, by replacing with congeners,using part of M³ instead of M′⁴⁺, and introducing the thinking of gapLi⁺, the inventor finds a novel sulfide solid electrolyte,Li_(2+x)M_(2+x)M′_(1−x)S₆. This kind of material does not containphosphorus, and has a low Li⁺ migration barrier, with great applicationpotential.

The embodiments of the application provide a solid electrolyte material.The general chemical formula of the material isLi_(2+x)M_(2+x)M′_(1−x)S₆, wherein M is at least one of Al, Ga or In, M′is at least one of Si or Ge, and 0<x≤0.5.

1. Structural Characteristics

The application firstly discloses the structural characteristics of theLi_(2+x)M_(2+x)M′_(1−x)S₆ material, which has diamond-like structuralcharacteristics. Lattice parameters are around a=13.0±2.0 Å, b=8.0±2.0Å, c=13.0±2.0 Å, α=90.0°±5°, β=110.0°±10°, and γ=90.0°±5°. For theLi_(2+x)Al_(2+x)Si_(1−x)S₆ in the application, lattice parameters areabout a=12.0±1.0 Å, b=7.0±1.0 Å, c=12.0±1.0 Å, α=90.0°±5°, β=105°±5°,and γ=90.0°±5°. Specifically, for a Li_(2.125)Al_(2.125)Si_(0.875)S₆material, lattice parameters are about a=11.7, b=7.2, c=11.6, α=90.3°,β=107.9°, and γ=89.7°; for a Li_(2.25)Al_(2.25)Si_(0.75)S₆ material,lattice parameters are about a=11.7, b=7.3, c=11.7, α=89.7°, β=107.5°,and γ=90.1°; for a Li_(2.5)Al_(2.5)Si_(0.5)S₆ material, latticeparameters are about a=12.0, b=7.6, c=11.8, α=88.5°, β=102.9°, andγ=90.2°. In the structure, coordination of M³ and M′⁴ with four S²⁻forms tetrahedrons. All connected corner-sharing tetrahedrons form athree-dimensional network, and Li⁺ is filled in the gap betweentetrahedrons. It can be seen from the composition and structuralcharacteristics of elements that Li_(2+x)M_(2+x)M′_(1−x)S₆ has goodstability.

2. XRD Spectrogram

The application also discloses characteristics of an XRD spectrogram ofthe Li_(2+x)M_(2+x)M′_(1−x)S₆ material. As shown in FIGS. 2, 6 and 10,in the XRD spectrogram, strong diffraction peaks may occur at about14.5°±3°, 15.5°±3°, 17°±3°, 25.5°±3°, 31.5°±3°, 53.0°±3°, or the like.Specifically, for the Li_(2.125)Al_(2.125)Si_(0.875)S₆ material, strongdiffraction peaks may occur at about 14.60, 16.00, 18.00, 26.00, 31.30,and 53.5°; for the Li_(2.25)Al_(2.25)Si_(0.75)S₆ material, strongdiffraction peaks may occur at about 14.60, 16.00, 17.70, 26.00, 31.10,and 53.40; for the Li_(2.5)Al_(2.5)Si_(0.5)S₆ material, strongdiffraction peaks may occur at about 14.0°, 15.4°, 16.8°, 25.4°, 30.8°,and 52.1°.

3. Lithium-Ion Transport Characteristics

Materials that can be used as solid electrolytes must meet theconditions of electronic insulation and ionic conductivity. It iswell-known that electronic insulation is greatly related to the opticalband gap of materials. Therefore, the invention uses PBEexchange-correlation functional for calculating the total density ofstates of several Li_(2+x)M_(2+x)M′_(1−x)S₆ materials (takingLi_(2.125)Al_(2.125)Si_(0.875)S₆, Li_(2.25)Al_(2.25)Si_(0.75)S₆, andLi_(2.5)Al_(2.5)Si_(0.5)S₆ as demonstrative examples). As shown in FIGS.3, 7, and 11, the PBE band gap of the Li_(2+x)Al_(2+x)Si_(1−x)S₆material is no less than 2.80 eV. It is well-known thatexchange-correlation functional in the form of PBE may severelyunderestimate the optical band gap of insulators and semiconductors(refer to the patent document, publication number: CN106684437A), andthe intrinsic band gap of the Li_(2+x)Al_(2+x)Si_(1−x)S₆ material shouldbe far beyond 2.8 eV. In 2012, Yin Wenlong, et al. (Yin et al.,“Synthesis, Structure, and Properties of Li₂In₂MQ₆ (M=Si, Ge; Q=S, Se):A New Series of IR Nonlinear Optical Materials”, 2012, InorganicChemistry, Volume 51, Pages 5839-5843) firstly reported the experimentalband gap of Li₂In₂SiS₆ is about 3.61 eV. In the invention, Li₂In₂SiS₆ iscalculated with the same parameters, and the PBE band gap is 2.08 eV. Itcan be seen from this that the intrinsic band gap ofLi_(2+x)Al_(2+x)Si_(1−x)S₆ should exceed about 4.3 eV. It is aninsulator with a wide energy gap, and is characterized in electricalinsulation. Wide energy gap width also indicates the low bonding-stateenergy, i.e., high oxidation potential, and indicates that the structurehas a wide electrochemical window at the same time, conducive to matchwith high-voltage positive electrode materials.

Lithium-ion transport characteristics are the most criticalcharacteristics of solid electrolytes. Therefore, the inventorcalculates Li⁺ migration path and migration barrier of theLi_(2+x)M_(2+x)M′_(1−x)S₆ material by using First Principle and VASPsoftware (Hafner research group of University of Vienna, ViennaAb-initio Simulation Package).

It's understandable that in the Li_(2+x)M_(2+x)M′_(1−x)S₆ material, Mand M′ can be arbitrarily selected from Al, Ga, In and Si, Gerespectively. In order to describe clearly and simply, the inventiontakes Li_(2+x)Al_(2+x)Si_(1−x)S₆ as an example to discuss, andexhaustively calculates Li⁺ migration path and migration barrier ofLi_(2.125)Al_(2.125)Si_(0.875)S₆, Li_(2.25)Al_(2.25)Si_(0.75)S₆,Li_(2.5)Al_(2.5)Si_(0.5)S₆, or the like.

FIGS. 1, 5, and 9 illustrate Li⁺ migration paths of theLi_(2+x)Al_(2+x)Si_(1−x)S₆ material, wherein gray Li⁺ ion is at atransition position artificially inserted between the initial state andthe final state, and Li⁺ transits from the initial state to the finalstate via the intermediate state. FIGS. 4, 8, and 12 illustrate themigration barrier shape of lowest activation energy in these migrationchannels through the further calculation of transition state.Specifically, the interstitial lithium-ion pushes the latticelithium-ion to the next gap site and occupies a lattice site, enablingLi⁺ transport by the means of “interstitialcy”. ForLi_(2.125)Al_(2.125)Si_(0.875)S₆, Li_(2.25)Al_(2.25)Si_(0.75)S₆, andLi_(2.5)Al_(2.5)Si_(0.5)S₆, the migration barrier is about 0.41, 0.34,and 0.25 eV respectively. As a contrast, it is reported in the document(Ceder et al., “First principles study of the Li₁₀GeP₂S₁₂ lithium superionic conductor material”, 2012, Chemistry of Materials, Volume 24,Pages 15-17. Mo et al., “Origin of fast ion diffusion in super-ionicconductors”, 2017, Nature Communications, Volume 8, Pages 15893.) thatLi⁺ migration barrier of LGPS material (benchmark material in sulfidesolid electrolyte) is about 0.2 eV. It can be seen from this that Li⁺ ina lattice structure of the Li_(2.5)Al_(2.5)Si_(0.5)S₆ material candiffuse easily, and this material is a good potential solid electrolytematerial.

It can be seen from the embodiments above that theLi_(2+x)M_(2+x)M′_(1−x)S₆ material disclosed by the invention does notcontain phosphorus, and is characterized in improved chemical stability,wide optical band gap (wide electrochemical window), and good Li⁺transport capability, thereby having great application potential.

II. Electrochemical Device

The electrochemical device according to the application includes anydevice that generates an electrochemical reaction, and specific examplesinclude all kinds of primary batteries, secondary batteries, fuelbatteries, solar batteries, or capacitors. Particularly, theelectrochemical device is a lithium secondary battery, including alithium metal secondary battery or a lithium-ion secondary battery. Insome embodiments, the electrochemical device according to theapplication includes a positive electrode, a negative electrode, and thesolid electrolyte of the application.

III. Application

The electrochemical devices manufactured according to the applicationare applicable to electronic equipment in various fields.

The electrochemical device according to the application is notparticularly limited in the purpose, and can be used for any purposeknown in the prior art. In one embodiment, the electrochemical deviceaccording to the application can be used for, including but not limitedto notebook computers, pen-type computers, mobile computers, e-bookplayers, portable phones, portable fax machines, portable copiers,portable printers, head-mounted stereo headsets, video recorders, liquidcrystal TVs, portable cleaners, portable CD players, mini disks,transceivers, electronic notebooks, calculators, memory cards, portablerecorders, radios, standby power supplies, motors, automobiles,motorcycles, power-assisted bicycles, bicycles, lighting appliances,toys, game machines, clocks, electric tools, flashlights, cameras, largehousehold batteries, and lithium-ion capacitors.

Embodiments

The description below is the performance evaluation according to theembodiments of the application.

1. Preparation and Performance Evaluation of Solid Electrolyte Materials

The Li_(2+x)M_(2+x)M′_(1−x)S₆ material disclosed by the invention can beprepared by many conventional methods. For instance, Li₂O, M₂O₃, andM′O₂ can be used as raw materials. They are mixed evenly according tothe required molar ratio, ground into the uniform powder by ball millingunder the protection of the inert atmosphere, and sintered by thehigh-temperature solid-state method under the inert atmosphere orvacuum. It can be understood that other preparation means can beselected, e.g., melt quenching. Certainly, appropriate target materialscan also be selected, and the solid electrolyte material is prepared byphysical or chemical vapor deposition. The expected element molar ratiocan be obtained by deposition by adjusting relevant process parameters.Since these preparation processes are familiar to those skilled in theart, they will not be repeated here.

2. Manufacturing of the Electrochemical Device

Some embodiments of the invention also provide a secondary battery,which can be a lithium-ion battery or a lithium metal battery. In thesecondary battery, the Li_(2+x)M_(2+x)M′_(1−x)S₆ material described inthe aforesaid embodiments of the invention can be used. Since thestructure of the solid secondary battery is familiar to those skilled inthe art, it will not be repeated here.

The embodiments above are demonstrative implementations of theinvention. The implementations of the invention are not limited by theembodiments above. The scope of the invention is only defined by theclaims attached and equivalents thereof.

What is claimed is:
 1. A solid electrolyte material, wherein a generalchemical formula of the material is Li_(2+x)M_(2+x)M′_(1−x)S₆, where Mis at least one of Al, Ga or In, M′ is at least one of Si or Ge, and0<x≤0.5.
 2. The solid electrolyte material according to claim 1, whereinM is Al and M′ is Si.
 3. The solid electrolyte material according toclaim 1, wherein lattice parameters thereof are about a=13.0±2.0 Å,b=8.0±2.0 Å, c=13.0±2.0 Å, α=90.0°±5°, β=110.0°±10°, and γ=90.0° 5°. 4.The solid electrolyte material according to claim 1, wherein latticeparameters thereof are about a=12.0±1.0 Å, b=7.0±1.0 Å, c=12.0±1.0 Å,α=90.0°±5°, β=105°±5°, and γ=90.0°±5°.
 5. The solid electrolyte materialaccording to claim 1, wherein the material has diamond-like structuralcharacteristics, coordination of M³⁺ and M′⁴⁺ in a structure with S²⁻forms tetrahedrons [MS₄] and [M′S₄], all corner-sharing tetrahedrons areconnected, and Li⁺ is filled in a gap between tetrahedrons.
 6. The solidelectrolyte material according to claim 1, wherein diffraction peaksoccur at about 14.5°±3°, 15.5°±3°, 17°±3°, 25.5°±3°, 31.5°±3°, or53.0°±3° in an XRD spectrogram.
 7. The solid electrolyte materialaccording to claim 2, wherein a Li⁺ migration barrier thereof is no lessthan about 0.45 eV.
 8. The solid electrolyte material according to claim2, wherein a PBE band gap thereof is no less than about 2.80 eV.
 9. Anelectrochemical device, comprising: a positive electrode, a negativeelectrode, and a solid electrolyte; the solid electrolyte comprises asolid electrolyte material, wherein a general chemical formula of thesolid electrolyte material is Li_(2+x)M_(2+x)M′_(1−x)S₆, where M is atleast one of Al, Ga or In, M′ is at least one of Si or Ge, and 0<x≤0.5.10. The electrochemical device according to claim 9, wherein M is Al andM′ is Si.
 11. An electronic device, comprising the electrochemicaldevice according to claim
 9. 12. The solid electrolyte materialaccording to claim 2, wherein the material has diamond-like structuralcharacteristics, coordination of M³⁺ and M′⁴⁺ in a structure with S²⁻forms tetrahedrons [MS₄] and [M′S₄], all corner-sharing tetrahedrons areconnected, and Li⁺ is filled in a gap between tetrahedrons.